1. Field of the Invention
The present invention relates to a random access method and apparatus in a wireless communication system.
2. Description of the Related Art
In a wireless communication system, research has been conducted to provide User Equipments (UEs) with high-speed services having various Qualities of Service (QoS). Representative examples of such a wireless communication system include a Long Term Evolution (LTE) wireless communication system, a wireless communication system using the 3rd Generation Partnership Project 2 (3GPP2) specification based on a Code Division Multiple Access (CDMA) scheme (herein after referred to as a “3 GPP2 wireless communication system”), a wireless communication system using the 3rd Generation Partnership Project (3GPP) specification based on a Wideband Code Division Multiple Access (WCDMA) scheme (herein after referred to as a “3GPP wireless communication system”), a Worldwide interoperability for Microwave Access (WiMAX) wireless communication system using the WiMAX forum network working group standard specification, an Institute of Electrical and Electronics Engineers (IEEE) 802.16m communication system, and the like.
A related-art random access method corresponds to a contention-based random access method in which a UE contends with other UEs for a Random Access CHannel (RACH) randomly assigned according to the RACH assignment scheme. When the contention-based random access method is used, random access is performed using one random access channel for each UE.
However, in the case of the related-art contention-based random access method using one random access channel, all UEs use only one random access channel respectively, and therefore the probability of network access success is the same for all the UEs.
As a result, since even a UE requiring relatively fast network access, such as a UE requesting an emergency call or a UE for which a handover is ongoing, must perform random access with the same probability of success, it is difficult to provide satisfactory service.
Accordingly, to address this problem, a contention-free random access method has been proposed in which a UE uses a random access channel predefined between the UE and a network to be accessed or a random access channel previously assigned to the UE through a connection establishment with a network to be accessed.
However, the contention-free random access method causes a problem in that fast network access cannot be provided because resource use is inefficient, a service delay occurs, and the like.
Therefore, there is a need for a new random access method that can significantly shorten a service connection delay or an initial service connection time through fast random access, and can also maintain efficiency of resource use by using one random access channel for a UE, which is being provided with a low-priority service, as in the related-art random access method.